Influence of Hypoxia Inducible Factor-1α of Endothelial Progenitor Cells on Left Ventricular Function in Experimental Myocardial Infarction

Based on the promotion of myocardial activity via endothelial progenitor cells (EPCs) subsequent to acute myocardial infarction (AMI), our research was designed to explore the influence of excessive HIF-1α expression in expanded EPCs (eEPCs) on promotion of the activity of left ventricle subsequent to MI. Isolation of EPCs from cord blood was performed before transduction with the help of retroviral vector with or without HIF-1α expression. Transplantation was performed subsequent to ligation of the left anterior descending coronary artery in mice. Ejection fraction (EF) of left ventricle was promoted via transplantation after 2 weeks. Excessive HIF-1α expression enhanced EF of left ventricle and decreased the extent of MI. It was revealed via functional studies that excessive HIF-1α expression enhanced proliferation of EPCs triggered by low oxygen concentration and suppressed cell death in the region of infarction. Moreover, markers of endothelium CD31, VEGF, and eNOS were upregulated. Transplantation of eEPCs with excessive HIF-1α expression in AMI can promote myocardial activities by increasing differentiation, generation of vessels, proliferation of eEPCs, and suppressing cell death. The above findings propose that regulation of EPCs via HIF-1α enhances the activity as well as mobilization of EPCs, indicating that reinforcement of expression of HIF-1α is beneficial for coronary heart disease.

Nrf2 attenuates the innate immune response after experimental myocardial infarction

Objectives: We aimed to investigate the contribution of the transcription factor nuclear factor erythroid-derived 2-like 2 (Nrf2) to the inflammatory response after experimental myocardial infarction (MI. Background: There is compelling evidence implicating dysregulated inflammation in the mechanism of ventricular remodeling and heart failure (HF) after MI. The transcription factor Nrf2 (encoded by Nfe2l2) is a promising target in this context. It impedes transcriptional upregulation of pro-inflammatory cytokines and is anti-inflammatory in various murine models. Methods: We subjected Nrf2-/- mice and wild type (WT) controls to permanent left coronary artery (LCA) ligation. The inflammatory response was investigated with fluorescence-activated cell sorting (FACS) analysis of peripheral blood and heart cell suspensions, together with qRT-PCR of infarcted tissue for chemokines and their receptors. To investigate whether Nrf2-mediated transcription is a dedicated function of leukocytes, we interrogated publicly available RNA-sequencing (RNA-seq) data from mouse hearts after permanent LCA ligation for Nrf2-regulated gene (NRG) expression. Results: FACS analysis demonstrated a profoundly inflamed phenotype in the hearts of global Nrf2-/- mice as compared to WT mice after MI. Moreover, infarcted tissue from Nrf2-/- mice displayed higher expression of inflammatory cytokines, chemokines, and their receptors, including IL6, Ccl2, and Cxcr4. RNA-seq analysis showed upregulated NRG expression in WT mice after MI compared to untreated mice, which was significantly higher in bioinformatically isolated CCR2+ cells. Conclusions: Taken together, the results suggest that Nrf2 signalling in leukocytes, and possibly CCR2+ monocyte-derived cardiac resident macrophages, may be potential targets to prevent post-MI ventricular remodeling.

The epicardial delivery of cardiosphere derived cells or their extracellular vesicles is safe but of limited value in experimental infarction

The epicardial administration of therapeutics via the pericardial sac offers an attractive route, since it is minimally invasive and carries no risks of coronary embolization. The aim of this study was to assess viability, safety and effectiveness of cardiosphere-derived cells (CDCs), their extracellular vesicles (EVs) or placebo administered via a mini-thoracotomy 72 h after experimental infarction in swine. The epicardial administration was completed successfully in all cases in a surgery time (knife-to-skin) below 30 min. No significant differences between groups were found in cardiac function parameters evaluated using magnetic resonance imaging before therapy and at the end of the study, despite a trend towards improved function in CDC-treated animals. Moreover, infarct size at 10 weeks was smaller in treated animals, albeit not significantly. Arrhythmia inducibility did not differ between groups. Pathological examination showed no differences, nor were there any pericardial adhesions evidenced in any case 10 weeks after surgery. These results show that the epicardial delivery of CDCs or their EVs is safe and technically easy 3 days after experimental myocardial infarction in swine, but it does not appear to have any beneficial effect on cardiac function. Our results do not support clinical translation of these therapies as implemented in this work.

Cardioprotective Role of SIRT5 in Response to Acute Ischemia Through a Novel Liver-Cardiac Crosstalk Mechanism

Protein posttranslational modifications play important roles in cardiovascular diseases. The authors’ previous report showed that the abundance of succinylated and glutarylated proteins was significantly lower in the serum of patients with acute myocardial infarction (AMI) than in that of healthy volunteers, suggesting a potential relationship between protein acylation and AMI. Sirtuin 5 (SIRT5) facilitates the removal of malonyl, succinyl, and glutaryl modification; however, its effects on AMI remain unknown. In this study, the levels of SIRT5 in AMI mouse model was compared. Results showed elevated hepatic SIRT5 after myocardial infarction. Hepatocyte-specific SIRT5 overexpressing mice (liver SIRT5 OE) were generated to address the possible involvement of hepatic SIRT5 in AMI. The areas of myocardial infarction, myocardial fibrosis, and cardiac function in a model of experimental myocardial infarction were compared between liver SIRT5 OE mice and wild-type (WT) mice. The liver SIRT5 OE mice showed a significantly smaller area of myocardial infarction and myocardial fibrosis than the WT mice. The fibroblast growth factor 21 (FGF21) in the blood and myocardium of liver SIRT5 OE mice after AMI was markedly elevated compared with that in WT mice. The results of mass spectrometry showed increased levels of proteins regulating tricarboxylic acid cycle, oxidative phosphorylation, and fatty acid β-oxidation pathways in the liver mitochondria of liver SIRT5 OE mice. These findings showed that SIRT5 may exhibit a cardioprotective effect in response to acute ischemia through a liver-cardiac crosstalk mechanism, probably by increasing the secretion of FGF21 and the improvement of energy metabolism.

Thrombus-targeting therapy with apyrase-annexin V fusion attenuates thrombosis without bleeding

Antithrombotic therapy is essential to prevent thrombotic reocclusion in patients with acute myocardial infarction, stroke, or venous thromboembolism. However, current antithrombotic drugs cause bleeding that limits dose and clinical effectiveness. Previously, we reported that APT102 (AZD3366), a human apyrase optimized to scavenge extracellular ADP and ATP, exhibited potent antiplatelet efficacy without bleeding in experimental myocardial infarction and stroke. Here we describe APT402, an optimized fusion of APT102 and annexin V that uniquely inhibits both platelet and coagulation components of thrombus growth. APT402 preferentially bound to injured vessels and thrombus and prevented thrombotic occlusion in arterial and venous thrombosis models, without increasing bleeding. Thus, APT402 breaks the confounding link between antithrombotic efficacy and bleeding, pioneering a safe and effective approach to prevent and treat a broad range of thrombotic diseases, and may be particularly useful in clinical conditions associated with high bleeding risks.

Protective Effects of Sacubitril/Valsartan on Cardiac Fibrosis and Function in Rats With Experimental Myocardial Infarction Involves Inhibition of Collagen Synthesis by Myocardial Fibroblasts Through Downregulating TGF-β1/Smads Pathway

Objectives: To investigate the effect and mechanism of sacubitril/valsartan on myocardial fibrosis in rats following experimental myocardial infarction and in TGF-β1-treated myocardial fibroblasts.Methods: Male Sprague-Dawley (SD) rats were subjected to coronary artery ligation to establish myocardial infarction and intragastrically fed vehicle, valsartan (Val, 32 mg/kg, once-daily) or sacubitril/valsartan (Sac/Val, 68 mg/kg, once-daily) for 4 weeks. In parallel, myocardial fibroblasts (MFs) isolated from neonatal SD rats were exposed to hypoxia and treated with TGF-β1 (5 ng/ml) plus vehicle, Val (107–10–5 M) or Sac/Val (107–105 M). Rat cardiac function and fibrosis were measured by echocardiography and histological method, respectively. MFs viability and collagen synthesis were determined by cell counting kit-8 and enzyme-linked immunosorbent assay, respectively. Protein expressions of TGF-β1, Smad3, phosphorylated Smad3 (p-Smad3), and p-Smad3 subcellular localization were detected by immunoblotting and immunocytochemistry.Results: Sac/Val significantly improved cardiac structure and function in rats after myocardial infarction, including decreased left ventricular end-diastolic diameter and interventricular septal thickness, increased ejection fraction, and reduced myocardial collagen volume fraction and type Ⅰ and type Ⅲ collagen levels, and this effect was superior to that of Val. Besides, Sac/Val inhibited myocardial TGF-β1 and p-Smad3 protein expression better than Val. Mechanically, Sac/Val significantly attenuated TGF-β1-induced proliferation and collagen synthesis of MFs, and inhibit Smad3 phosphorylation and nucleus translocation, and this effect outperformed Val. Overexpression and silencing of Smad3 enhanced and reversed the inhibitory effects of Sac/Val on TGF-β1-induced collagen synthesis by MFs, respectively.Conclusions: Sacubitril/valsartan improves cardiac function and fibrosis in rats after experimental myocardial infarction, and this effect is related to the inhibition of collagen synthesis in myocardial fibroblasts by inhibiting the TGF/Smads signaling pathway.

Epicardial Delivery of Cardiosphere Derived Cells or Their Extracellular Vesicles in a Relevant Infarcted Swine Model: Safe, Easy but of Limited Effectiveness.

The epicardial administration of therapeutics via the pericardial sac offers an attractive route, since it is minimally invasive and carries no risks of coronary embolization. The aim of this study was to assess viability, safety and effectiveness of Cardiosphere-Derived Cells (CDCs), their extracellular vesicles (EVs) or placebo administered via a mini-thoracotomy 72h after experimental infarction in swine. The epicardial administration was completed successfully in all cases in a surgery time (knife-to-skin) below 30 minutes. No significant differences between groups were found in cardiac function parameters evaluated using magnetic resonance imaging before therapy and at the end of the study, despite a trend towards improved function in CDC-treated animals. Moreover, infarct size at 10 weeks was smaller in treated animals, albeit not significantly. Arrhythmia inducibility did not differ between groups. Pathological examination showed no differences, nor were there any pericardial adhesions evidenced in any case 10 weeks after surgery. These results show that the epicardial delivery of CDCs or their EVs is safe and technically easy 3 days after experimental myocardial infarction in swine, but it does not appear to have any beneficial effect on cardiac function. Our results do not support clinical translation of these therapies as implemented in this work.